1. Field of the Invention
The present application relates to seismic safety valves and a valve actuator therefore. In particular, it relates to valves used to shutoff the supply of gas to a structure in the event of an earthquake and how such valves are actuated.
2. State of the Prior Art
Various devices have been known in the prior art for shutting off gas systems in the event of a seismic disturbance. For example, U.S. Pat. Nos. 4,311,171, 4,565,208, and 4,475,565 all illustrate different types of valves designed to shutoff the flow of gas in the event of a seismic disturbance.
Applicant's own prior valves and systems include those in U.S. Pat. Nos. 4,903,720, 5,119,841, 5,409,031, 6,085,772 and 6,705,340. These different patents address various concerns with respect to shutting off the flow of natural gas to a point of use in the event of a seismic disturbance. These patents also recognize that other disturbances might be appropriate in triggering the shutoff of gas. They have in common the concept of shutting off the flow of gas exterior to the point of use structure. For example, the shutoff valve may be positioned at or near the gas meter on the exterior of the point of use structure.
The present inventor has recognized, however, that in some prior valve installations that are currently on the market, a number of problems exist. For example, in prior valves, the sensor mechanism that detects seismic activity to trigger the shutoff of the valve is incorporated with the valve itself. This then requires the valve to be level. It further requires the valve itself to be braced to the structure, i.e. to be directly fixed with the structure that is the point of use, for proper sensing of the seismic activity. This requires rigid bracing to be provided, which increases the likelihood of the piping breaking before the valve in the event of seismic activity. The labor cost is thus high in the installation of the valve.
Prior art valves also require additional fittings to be installed, are not adaptable to “smart” controls, and are limited to the earthquake market only. Further, they will not work with water. The meter usually needs to be displaced for the installation, and the valve structure itself often results in poor flow of the gas.
Additionally, the present inventor has recognized that the prior art valves do not have such desirable features as a manual shutoff. They also lack a positive “off”; in other words, the valve can reset by itself after shutting off. The status indicators of the prior art valves also tend to be hard to read, and there tend to be too many false triggers of the valve.